The present invention first of all relates to a device for controlling the closing and opening of the extraction chamber of a coffeemaking machine.
The invention also relates to a process for the control of the closing of the extraction chamber.
This device and this process find particular use in coffeemaking machines of the espresso type for domestic or professional use.
Essentially, the coffeemaking machines in question are machines in which the extraction chamber comprises two portions movable relative to each other. This movement is provided by an electric motor to open or close the extraction chamber.
It should be remembered that the extraction chamber delimits an internal volume adapted to receive a dose of ground coffee from which will be extracted the coffee beverage.
A particular application will consist in using the present invention in coffeemaking machines adapted to receive prepackaged doses of ground coffee.
These prepackaged doses of ground coffee will hereinafter be called small doses.
According to the present state of the art, it is necessary to operate different phases of opening and closing the extraction chamber to permit the operation of the coffeemaking machine.
Thus, in a first instance, the ground coffee must be introduced into the extraction chamber, which requires its opening.
Then, before starting forced steeping, the extraction chamber must be closed in a sealed manner.
At present, the closed position of the extraction chamber is detected by the bias of a position detector placed on the motor member or on a movable element whose position reveals the closing of the extraction chamber.
It must be noted that this type of closure detection has various drawbacks.
In the first place, there is no adaptation of the detection to varying possible dimensions of the pieces constituting the machine.
Thus, in the case of play, dimensional variations due to the tolerances of production, or the like, the optimum closed position of the extraction chamber can change without this being detected by a position detector.
Moreover, in the particular case of the use of small doses, the latter can also have dimensional variations.
In particular, certain small doses have a rigid periphery permitting reinforcing the small dose and taking part in sealing of the extraction chamber during extraction of the coffee.
The rigid periphery of such small doses can have great dimensional variations.
As a result, according to the present state of the art, the locking of the extraction chamber cannot be optimum.
Thus, the detection of closure by a position detector can be triggered too soon, which stops the motor prematurely.
Moreover, the end of locking can be delayed (triggering the position detector after the optimum closure position), which may lead to wear on the pieces, bad locking or else a useless overconsumption of electrical energy.
The present invention has for its object to overcome the drawbacks of the present state of the art as to this.
One of its first objects is to permit a perfect positioning of the two movable parts comprising the extraction chamber in the closed position.
Thus, the alignment of the edges of the movable portions will be an optimum, thereby ensuring good sealing and avoiding any wear.
The locking must itself also be effective to avoid any loss and to use all the power of the motor for closing.
Moreover, perfect stopping of the motor will permit a drop in the consumption of energy supplied to the motor.
Finally, even in the case of large dimensional variations of the pieces or of the small doses, an immediate adaptation of the device will be effectuated.
Moreover, the invention also ensures relocking of the chamber in the course of steeping to maintain the optimim seal throughout the cycle.
The present invention relates to a device for controlling the closing and opening of the extraction chamber of a coffeemaking machine of the espresso type, said extraction chamber comprising two portions movable relative to each other by an electric motor to open or close the extraction chamber, characterized by the fact that it has:
means for measuring the intensity of the current supplied to the motor at least during the closing phase of the extraction chamber;
means for detecting a drop in the derivative relative to time, of the supply current, below a predetermined threshold, permitting detecting the optimum closed position for the extraction chamber, so as to stop the movement of the movable parts when this position is reached.
This device can have different modes of embodiment, among which are the following:
the measuring means have:
a measuring electric resistance, at the terminals of which the voltage VR is proportional to the value of the current supply to the motor,
an assembly with a non-inverting operational amplifier permitting amplifying the voltage VR at the terminals of the measuring resistance,
so as to obtain an electrical quantity reflecting the supply current for use by the detection means.
It comprises an analog-digital converter for the conversion of the electrical supply current or of the electrical quantity reflecting it, into a digital quantity.
The detection means comprise a microprocessor with an inlet terminal which receives the digital value reflecting the supply current, and a computation program for the derivative relative to time of said current or of said electrical quantity.
The detection means comprise at least one control output of the electric motor according to the value of the derivative relative to time.
It comprises a position detector permitting detecting the open position of the extraction chamber according to the angular position of the motor or of the transmission gearing.
It comprises at least one detector for the presence of a small dose.
It comprises a detector detecting the presence of a small dose in upper position and a detector detecting the presence of a small dose in a lower position.
It comprises a position detector and a solid plate for transmission gearing, said plate being divided into two half discs of different radii and the plate is positioned on the gearing such that the transition fronts between the two half discs pass respectively facing the position detector when the extraction chamber is in the open position and when the extraction chamber is in a maximum closed position.
The invention also relates to a process for the control of the closing of the extraction chamber of a coffeemaking machine of the espresso type, said extraction chamber comprising two portions movable relative to each other by an electric motor to open or close the extraction chamber, said process being adapted to be practiced by the device, characterized by the fact that
there is measured, at least during the closing phase of the extraction chamber, the intensity of the current supplying the motor,
there is detected a drop in the derivative relative to time, of the supply intensity, below a predetermined threshold, to detect the optimum closed position of the extraction chamber, so as to stop the movement of the movable portions when this position is reached.
This process comprises the following preferred embodiments:
The intensity of the measured supply current is processed so as to obtain a numerical quantity reflecting said intensity.
The drop in the derivative relative to time, of the supply intensity, is detected by carrying out iteratively he following steps:
the value of the numerical quantity is taken at two times separated by a fixed time interval
the slope of the straight line passing through the two points defined by their time abscissae and their ordinates of the value of the numerical quantity, is calculated.
The motor is stopped when the slope of the straight line passes below the predetermined threshold for a predetermined number of iterations.
In the course of extraction, there is carried out a supplemental closing movement of the extraction chamber.
The supplemental movement of closing is sequential.
The supplemental closing movement is prolonged until the end of the extraction or until obtaining a maximum closed position of the extraction chamber.